Search

Crees pour certains depuis plus de quarante ans, les bases de donnees et les reseaux de reference en elevage sont devenus des outils indispensables au conseil et des supports precieux pour la formation et la recherche. Face aux nouveaux defis auxquels est confronte l'elevage et dans un contexte budgetaire contraint, il importe de les preserver tout en les faisant evoluer pour mieux repondre aux nouvelles attentes et pour optimiser les moyens mobilises.

A ce jour pas de Clé UT; International audience; Four early lactating Holstein cows were used to study the effect of live yeast (LY, Actisaf® CNCM I-4407, Lesaffre Feed Additives, Marcq en Baroeul, France) supplementation on diet digestive utilization of dairy cows receiving concentrated corn silage-based diets with two rumen-degradable protein (RDP) levels. For a 33 d period, cows were fed a total mixed ration (TMR) containing an adequate level (AL) of RDP or a low level (LL, 30% below AL) by using soybean meal or tanned soybean meal, respectively: for 21 d with no LY addition followed by 12 d during which LY was added to the diet. The pH and redox potential (Eh) were recorded and ruminal fluid samples were collected over 3 consecutive days. Feces were collected individually over 48 h and individual dry matter intake (DMI) was measured for determining apparent nutrient digestibility. The effective degradability of individual feed ingredients composing both diets was evaluated with nylon bags technique. Structure of the ruminal bacterial community was studied and diversity index was calculated. Digestibility of organic matter (OM) and crude protein (CP) were lower for LL than those for AL. With LY, digestibility of OM and CP was increased: +2.4 and +0.8 points, for AL, and +3.7 and +5.9 points for LL, respectively. Live yeast reduced dietary N ruminal degradation with both AL and LL. Ruminal pH and Eh were lower with AL compared to LL: 5.95 and –167 mV vs. 6.13 and –144 mV. Live yeast increased ruminal total volatile fatty acids (VFA) (+8.6%), C2 (+10%), and C4 (+35%) contents for LL and decreased that of C3 (−9.8%) for AL. Neither the structure of bacterial populations of the rumen nor the diversity index (Shannon) was altered by treatments. Those results suggested a specific interest in using LY in RDP deficient diets for early lactating cows.

Suite à un appel d’offre du Commissariat Général à la Stratégie et à la Prospective du gouvernement français, l’INRA a analysé les possibilités d’évolution des pratiques et des systèmes agricoles français vers des systèmes de production plus durables conciliant performances productives, économiques, environnementales et sociales. Une méthodologie d’aide à la conception et à l’évaluation de systèmes a été développée à cette occasion. Elle s’appuie sur un répertoire de plus de 200 pratiques agricoles élémentaires dont l’impact a été qualifié sur 35 indicateurs de performances, ainsi que sur une table de compatibilité entre pratiques élémentaires. Deux études de cas fondées sur des modalités différentes d’utilisation de cette méthodologie sont présentées : i) la conception pas à pas de système de production par incorporation progressive de pratiques élémentaires à partir d’une pratique d’entrée à effet majeur, pour accroître l’autonomie alimentaire en production bovine laitière en valorisant la prairie ; ii) l’évaluation à postériori des performances de systèmes en transcrivant sous forme de pratiques élémentaires des leviers d’action et marges de progrès identifiés à dire d’expert pour améliorer la compétitivité de la filière poulet de chair par la mise en place de deux systèmes de production très contrastés mais complémentaires. Les tendances d’évolution des performances des systèmes de production ainsi simulés ou reconstitués sont discutées. Dans les situations d’impact ambivalent d’une pratique sur une performance, le recours au descriptif détaillé des pratiques permet le plus souvent de réduire l’incertitude en prenant en compte les situations associées à chaque type d’impact., Following the bidding by the General Commission for Future Strategy of the French government, INRA has analyzed the different evolutions possible in French practices and agriculture systems towards a more sustainable production that manages to combine productive, economic, environmental and social performances. A method to help design and evaluating the systems was thus developed. This method is based on over 200 basic agricultural practices whose impact was qualified on 35 performance indicators as well as on a compatibility index between these elementary practices. Two studies based on different uses of this method are presented: i) the step by step conception of a production system by progressively incorporating elementary practices from one entry practice with major effect, to increase food autonomy in dairy cattle production by valorizing grasslands; ii) evaluating the system performances a posteriori by transcribing the action levers and progress margins identified by an expert panel into elementary practices in order to improve competition of the broiler industry through the development of two very different but complementary production systems. The tendencies of the simulated or rebuilt performance evolution of these production systems are discussed. When situations present an ambivalent impact of a practice on one performance, using the detailed description of these practices often allows reducing the uncertainty by considering the situations associated with each type of impact.

L’acidose latente constitue aujourd’hui une cause d’inefficacité zootechnique des rations bien établie et est de ce fait l’une des préoccupations majeure pour la nutrition moderne des ruminants à haut potentiel. Les vaches laitières sont amenées à traiter des quantités très importantes de matière organique rapidement fermentescible dans le rumen ce qui met en péril le contrôle de l’acidité ruminale et à terme l’homéostasie de l’animal. Les facteurs à risques sont maintenant bien connus. Au premier rang figurent le niveau d’ingestion, les glucides à dégradation rapide et le hachage excessif des ensilages de maïs. S’il n’est pas toujours souhaitable de réduire le niveau d’ingestion, on peut réduire les risques en limitant les niveaux d’apport de glucides à dégradation très rapide (blé, orge, pulpes) et en veillant à la présentation physique du fourrage. Il n’y a malheureusement pas encore de systèmes permettant de raisonner précisément les rations sur la combinaison de ces facteurs. Les rations infra-optimales peuvent être sécurisées par la distribution de tampons. Plus récemment, il est apparu que l’enrichissement en cations et le niveau d’apport de protéines sont aussi des facteurs de sécurisation des rations. La gestion des risques d’apparition d’acidose latente doit être préventive et passe par un meilleur équilibre global de la ration. En l’absence d’un système fiable de prévision des zones à risques, il est préférable de ne pas incorporer plus de 20 % de glucides rapidement dégradables dans la ration surtout si leur bilan électrolytique est faible, ce qui est le cas du blé, de l’orge et les pulpes de citrus et veiller à ce que le fourrage rendu dans l’auge ne soit pas haché trop finement. Les rations peuvent également être sécurisées par l’apport de substances tampon à raison de 1 % de la MS et /ou par un apport de cations permettant d’atteindre un bilan électrolytique proche de 200 mEq/kg MS ainsi que par le maintien d’un niveau d’apport protéique proche de 100 g PDIE/UFL. Ces précautions apparaissent plus efficaces pour gérer les excès d’acidité que l’incorporation de paille dans la ration. Il n’est pas non plus nécessaire d’apporter des protéines dégradables en excès ce qui n’aura d’autre effet que d’accroître les rejets azotés.

Les prairies et le pâturage devraient constituer à l’avenir la base des systèmes laitiers durables. L’herbe pâturée est le fourrage le moins coûteux pour alimenter les vaches laitières et constitue un mode d’alimentation qui réduit l’impact environnemental des systèmes très intensifs tout en conférant une image plus « naturelle » aux systèmes laitiers. L’utilisation efficace de l’herbe au pâturage nécessite la mise au point de méthodes qui permettent de maximiser l’ingestion journalière d’herbe tout en assurant la production d’une quantité importante d’une herbe de qualité durant toute la saison de pâturage. Les opportunités d’accroître la part de l’herbe pâturée dans l’alimentation des vaches laitières existent en allongeant la saison de pâturage au printemps et/ou en automne et en pratiquant le report d’herbe sur pied en été. A ce titre, l’introduction de légumineuses, trèfle blanc notamment, dans les prairies doit être favorisée. Les possibilités de moduler la saisonnalité de la croissance de l’herbe existent au travers de la sélection fourragère, de la stratégie de fertilisation azotée ou des pratiques de pâturage. L’intérêt d’une réduction du chargement visant à maximiser les performances individuelles reste limité compte tenu des effets cumulatifs défavorables sur la qualité de l’herbe et sa valorisation. Par contre, l’accroissement de la proportion de feuilles grâce à des pratiques de pâturage appropriées au printemps permet d’accroître l’ingestion et de maintenir une hauteur résiduelle faible qui facilite la gestion du pâturage. Il reste à en évaluer les conséquences durant toute la saison de pâturage et son influence sur les performances annuelles par hectare. Dans un futur proche, le développement de méthodes et d’outils d’aide à la gestion du pâturage à la fois pour le rationnement des vaches laitières et pour la gestion des parcelles devrait donner confiance aux éleveurs et favoriser le retour du pâturage dans l’alimentation des vaches laitières., Utilisation of grazed grass should form the basis of sustainable dairy systems in the future. Grazed grass is the cheapest feed available for dairy cows and may also help to reduce the environmental impact of the most intensive systems while giving a natural image of farming. Efficient exploitation of grass by grazing will require the development of grazing systems designed to maximise daily herbage intake per cow while maintaining a greater quantity of high quality pasture over the grazing season. This paper discusses the conditions for efficient exploitation of grass and outlines the possibilities for future advances. There are opportunities to consume more grass by extending the grazing season in early spring and late autumn or by intentionally deferring grazing from a period of grass surplus in the spring to a period of grass shortage in the summer. The introduction of legumes in grass-based swards should also be seriously considered as an alternative option to pure grass swards in order to maximise cow performance. There are also opportunities to manage seasonal production of grass by plant selection, improved N fertilisation strategies and better grazing management. The opportunity to increase cow performance by decreasing stocking rates is rather limited because this practise is constrained by the necessity to maintain high quality swards over the grazing season, unless alternative strategies are adopted. Increasing leaf blade mass at the base of the sward by appropriate grazing management in the early spring may play a major role in increasing herbage intake. This will result in a low residual sward height thus making grazing management easier. This requires a greater knowledge of the carryover effects of early season grazing management on mid-season pasture quality and the implication for milk output per hectare. In the future, development of reliable decision support methods and tools for short term rationing of grass at the paddock level and long term budgeting of grass at the farm level will give farmers more confidence in grazing and will undoubtedly contribute to optimising the proportion of grazed grass in the annual diet of the dairy cow.

L’herbe pâturée est un fourrage de valeur nutritive élevée, peu coûteux à produire et à récolter et qui peut constituer le seul aliment de la ration de la vache laitière. En l’absence de toute complémentation, la production et la composition du lait d’une vache laitière au pâturage dépend d’abord de l’animal et de son potentiel au moment de la mise à l’herbe. Mais les conditions de pâturage (chargement, hauteur en début et fin de parcelle) imposées par l’éleveur pour valoriser au mieux l’herbe produite ne permettent pas aux vaches laitières de satisfaire la totalité de leurs besoins énergétiques. En conséquence, l’apport de concentré est aujourd’hui plus efficace que par le passé et des réponses de 1 kg de lait par kg de concentré, accompagnées d’une baisse du taux butyreux et d’une augmentation du taux protéique, sont souvent rapportées. Les travaux récents conduits à l’INRA montrent que cette efficacité varie peu dans les conditions habituelles de pâturage. De même, dans le cas d’apport identique de concentré entre vaches, l’efficacité semble indépendante du niveau de production entre 25 et 45 kg de lait par jour à la mise à l’herbe. Ces résultats permettent de proposer des simplifications dans les modalités d’attribution du concentré au pâturage. Comme en alimentation hivernale, la nature de l’énergie du concentré n’a réellement d’influence sur la composition du lait (taux butyreux) que pour des quantités élevées, supérieures à 5 kg de concentré. L’incorporation de matières premières riches en protéines, même protégées, ne se justifie que dans le cas d’herbe pâturée pauvre en azote. L’apport de fourrages complémentaires au pâturage présente peu d’intérêt et, dans la pratique, contribue souvent à une dégradation des conditions de pâturage. Seules les situations de pénurie fourragère ou de chargement très élevé permettent de bien valoriser à la fois l’herbe pâturée et les fourrages conservés distribués en complément., Grazed grass is a high nutritive value forage, inexpensive to produce and harvest and can be the only feed for a lactating dairy cow. Without supplementation, milk production and composition at grazing vary between animals and are dependant on cow genetic merit. But grazing conditions (stocking rate, pre- and post-grazing height) imposed by the farmer to improve grass utilisation does not allow the dairy cow to satisfy the total energy demand. Consequently, concentrate is now more efficient than in the past and often responses of one kg of milk to one kg of concentrate with declining milk fat content and increasing milk protein content are reported. Recent work at INRA has highlighted small variations in efficiency with different imposed grazing managements. At the same time, in the case of constant concentrate allocation, the efficiency is quite stable between cows producing 25 to 45 kg at turnout. With these results, it is possible to simplify the concentrate allocation method at grazing. As in winter feeding, the energy source of the concentrate has an influence on milk fat content but only at a high level of supplementation. Including protein rich ingredients, even protected, is only justified in the case of low crude protein content grass. Forage feeding at pasture is not necessary and can contribute to poor grass utilisation. Grazed grass and forage supplementation are well complemented only in periods of grass shortage or with very high stocking rates.

International audience; Fresh grass is often a fodder of high nutritive value for ruminants, but its intake is limited in spite of its high digestibility. The high water content of fresh grass could limit grass DM intake by cows. The effect of external water on intake, feeding behaviour and rumen fill was studied in dairy cows fed indoors with fresh perennial ryegrass offered ad libitum. Three treatments were compared: fresh grass as harvested (C: control); C with water added to the grass (SW: surface water) and C with perfusion of water in the rumen after each distribution (PW: perfused water). Grass was offered to cows at 14:00 h, 19:00 h on each day and 07:00 h the following morning. Free access was given to drinking water. In treatment SW, the DM content of the offered grass was reduced from 161 to 117 g$\cdot$kg$^{-1}$ on a fresh basis ($P < 0.02$) without changing the chemical composition of the grass on a DM basis. Compared to C and PW, the fresh matter intake and its rate of intake increased in SW (+ 36 and 39%, respectively), but the grass DM intake (16.4 kg DM$\cdot$day$^{-1}$), the rate of DM intake (35.3 g DM$\cdot$min$^{-1}$), the daily eating time (468 min) and rumination time (515 min) were not modified. Perfusion of water into the rumen did not affect intake or feeding behaviour. The weight of the rumen contents (150 kg) and their DM content (115 g$\cdot$kg$^{-1}$ fresh matter), rumen fluid osmolality, as well as proportions of free water and bound water and turnover rate were not modified by the treatments. In conclusion, for dairy cows fed on grass, important inputs of external water do not affect feeding behaviour, rumen fill nor grass DM intake.; L'addition d'eau externe à l'herbe verte n'affecte pas la quantité de matière sèche ingérée, le comportement alimentaire ou les caractéristiques du rumen chez la vache laitière. L'herbe fraîche est un aliment de bonne valeur alimentaire pour les ruminants mais son ingestion par les vaches laitières reste limitée au regard de sa digestibilité. La forte teneur en eau de l'herbe fraîche pourrait limiter la quantité ingérée de MS d'herbe. L'effet de l'eau externe à la plante sur l'ingestion, le comportement alimentaire et l'encombrement ruminal a été étudié sur des vaches laitières nourries à l'auge avec du ray-grass anglais distribué ad libitum. Trois traitements ont été comparés : herbe verte témoin, fauchée une fois par jour (C) ; C plus de l'eau ajoutée sur l'herbe (SW) et C plus perfusion d'eau dans le rumen après chaque distribution (PW). La distribution d'herbe a été faite à 14:00 h, 19:00 h et 07:00 h le lendemain matin. L'eau de boisson était en accès libre. Dans le traitement SW, la teneur en MS de l'herbe offerte a été réduite de 161 à 117 g$\cdot$kg$^{-1}$ brut ($P < 0,02$) sans changer la composition chimique de l'herbe. Par rapport à C et PW, la quantité brute ingérée d'herbe et la vitesse d'ingestion en brut ont fortement augmenté (respectivement + 36 et 39 %), mais la quantité de MS d'herbe ingérée (16,4 kg MS$\cdot$j$^{-1}$), la vitesse d'ingestion de MS (35,3 g MS$\cdot$min$^{-1}$) et les durées journalières d'ingestion (468 min) et de rumination (515 min) n'ont pas été modifiées. Perfuser l'eau dans le rumen n'a affecté ni l'ingestion ni le comportement alimentaire. Le poids total du contenu du rumen (150 kg), la teneur en MS du contenu (115 g$\cdot$kg$^{-1}$), l'osmolarité du liquide ruminal, la proportion d'eau libre et d'eau liée ainsi que le taux de renouvellement des liquides n'ont pas été modifiés par les traitements. En conclusion, pour des vaches en production nourries à l'herbe, un apport même important d'eau externe ne constitue pas de limite à la prise alimentaire, ni à l'encombrement dans le rumen, et n'affecte pas la quantité de MS d'herbe ingérée.

The objective of the trial was to analyse the effects of the mechanical resistance of cell walls and chewing behaviour on the proportion of intracellular constituents (ICs) released during the ingestive mastication of fresh perennial ryegrass (Lolium perenne L.) by steers. The mechanical resis- tance of cell walls was varied by the stage of maturity (15 vs. 30 days of regrowth). Herbage was of- fered at two chop lengths (long and short) for each stage of maturity, to influence chewing behaviour. Four steers, each fitted with a large ruminal cannula, were fed indoors with the ryegrass in a 4 × 4 Latin square design. Ingested boli were collected at the cardia and their IC contents were compared with the IC contents of the grass. The average shear energy was lower with the young grass because of a lower proportion of stems and pseudostems. The eating time per unit of dry matter intake was unaf- fected by the stage of maturity, but was slightly lower with the short herbages. The nature of the ICs had a strong effect on their release with the larger molecules, or the molecules contained in the chloroplasts, being less rapidly released. The ICs released (as a proportion of intake) ranged from 0.166 for the chlorophyll to 0.612 for the nitrates. The treatments had no effect on the rate of release of the small vacuolar or cytoplasmic ICs. The intracellular nitrogenous fractions, partly in the chloroplast, were released faster in the mature grass, because the animals had to masticate more inten- sively to obtain a 'swallowable'bolus due to it having a higher shear energy. The release of ICs did not seem to be dependent on the duration of chewing but rather on other parameters of mastication like the force exerted by the jaws, the surface-area of the molars, or the quantity of grass eaten per bolus. rumen digestion / water soluble carbohydrates / nitrogenous compounds / mastication / shear strength

The objective of this study was to examine the effect of the level of reducing nitrogen (N) fertiliser rate on herbage intake and N balance of dairy cows grazing a pure perennial ryegrass pas- ture. The addition of a protein supplement to cows grazing the low N fertilised sward was also evalu- ated. Three treatments were compared over three periods of 2 weeks using 9 fistulated cows in a 3 × 3 Latin square design: HN (80 kg N·ha -1 ·regrowth -1 ), LN (0-20 kg N·ha -1 ·regrowth -1 ), LN+S (LN + 2 kg of soybean meal (SBM)). Daily herbage organic matter (OM) intake was estimated by chromic oxide dilution in the faeces. Nitrogen and ADF contents in faecal OM were used to estimate the herb- age digestibility. Herbage mass, grazing behaviour and rumen fermentation pattern were measured. Nitrogen intake was estimated by the chemical composition of the defoliated herbage and urinary N was calculated by subtracting milk N and faecal N output from N intake. Digestibility (0.79), daily in- take (16.4 kg OM), grazing time (512 min) and the proportion of volatile fatty acid were not affected by reducing the N fertiliser rate. These results may be explained by the moderate effect of N fertilisa- tion on herbage mass which remained high in the LN swards (3.9 vs. 4.7 t OM·ha -1 for HN) and the rather large herbage allowance which allowed the cows to graze a herbage with a crude protein con- tent that still remained higher than 160 g·kg -1 DM. On the LN sward, N intake was significantly lower (- 80 g·d -1 )( P < 0.01), faecal N and milk N output remained unchanged, whereas urine N output de- creased (- 77 g·d -1 )( P < 0.01). Protein supplementation did not depress HOMI or grazing time, sup- plemented cows consumed 2.4 kg OM more (P < 0.01) and this increased milk yield by 1.3 kg·kg -1 SBM (P < 0.01). SBM supplementation largely increased N intake, and finally N excreted in the urine. It was concluded that N fertilisation, and N supplementation are efficient means to manipulate animal performances and N balance in grazing dairy cows.

EsCo : Elevage et Azote. Les flux d’azote liés aux élevages. Réduire les pertes, rétablir les équilibres; The nitrogen efficiency is the ratio between the output of nitrogen in the animal products and the input required for the livestock production. This ratio is a driver of the economic profitability and can be calculated at various levels of the production system: animal, field or farm. Calculated at the scale of the animal, it is generally low with less than half-ingested nitrogen remaining in the milk, the eggs or the meat in the form of proteins; the major part of the nitrogen being rejected in the environment. Significant gains were achieved in the past via the genetic improvement and the adjustment of feed supply. At the farm level, the efficiency increases to 45% to 50%, thanks to the recycling of animal excreta as fertilisers. From excretion to land application of manure, the losses of nitrogen are very variable depending on the animal species and the manure management system. Considering the risks of pollution swapping, all management and handling steps need to be considered. Collective initiatives or local rules on agricultural practices allow new opportunities to restore nitrogen balances on local territory.

La prairie est une surface multifonctionnelle qui procure à la fois une ressource alimentaire bon marché pour l'élevage de ruminants et des biens et services publics qui sont de mieux en mieux décrits par la recherche mais cette production de biens publics n'est pas, ou peu, rémunérée par les marchés (prix) ou par les politiques publiques (PAC). Les surfaces en prairie continuent donc de s'éroder. C'est donc par son aptitude à convaincre pour ses atouts économiques, les économies d' intrants qu'elle peut procurer, sa valeur alimentaire équilibrée et sa capacité productive annuelle que la prairie pourra se maintenir. Ce texte fait le point sur ces différents aspects et montre dans quelle mesure les nouvelles connaissances permettent d'envisager, grâce à une utilisation rationnelle de la prairie, des gains simultanés sur la productivité des surfaces, l'autonomie des systèmes et leurs performances environnementales., Since it has no market value, and is rarely granted public subsidies (CAP), land put down to grass has long been declining in France. This is particularly true of plains. Yet a large number of studies have shown that grass-based systems provide substantial benefits: nutritionally balanced forage and grass, improved financial performance owing to lower working costs, reliable, resilient, and sustainable systems (for example by limiting the use of imported soybean meal and optimizing land use), environmental benefits encouraged by sustainable farming practices (cover crops, fertilization), as well as rendered services... This new knowledge makes it possible to envisage a rational utilization of grassland that would optimize land use, self-sufficiency and environmental performance, thereby contributing to the development of high performance integrated farming systems.

absent

Séance : Environnement; Dans le cadre du projet européen RedNex, un outil de calcul des restitutions d’azote des vaches et génisses laitières (NexDairy) a été développé afin d’intégrer les séquences et pratiques alimentaires spécifiques de chaque élevage. Selon d’une part la composition de ces rations et la teneur en azote des ingrédients et d’autre part leurs niveaux d’ingestion estimés à partir des performances et de la capacité d’ingestion des animaux, les quantités d’azote ingérées, fixées chez l’animal en croissance ou exportées dans le lait, et les quantités excrétées dans les déjections sont calculées. Cette méthode d’évaluation des rejets azotés a été testée en élevage par les organismes de Conseil Elevage de Franche Comté qui disposent de l’ensemble des données nécessaires au modèle. Cette analyse à l’échelle du troupeau et de son alimentation permet de bien coller à la réalité de l’élevage concerné et d’évaluer les sources d’inefficacité et les marges de progrès possibles sur l’un des 3 postes essentiels (animal-troupeau / bâtiment-stockage / sol-plante) du cycle de l’azote en élevage.

Grass intake by growing horses at pasture: a test of the effects of the horses' age and sward biomass. No data are currently available on the quantities of food ingested by young horses at pasture, in spite of the fact that pasture constitutes the main source of nutrients for these animals. In this study, three levels of sward mass were offered to animals (2.3; 2.9 and 3.5 T DM .ha -1 ), which correspond to grass heights of 6.6, 8.1 and 9.4 cm. Horses of the Cheval de Selle Francais breed were used (1 and 2 years old, live weight of 334 and 478 kg respectively) in a latin square design. The daily quantities of grass ingested at pasture were determined, and relationships between daily intake, and the characteristics of the pasture and animal were studied. Intake relative to metabolic live weight did not vary between yearlings and 2-year-old horses. Intake averaged 82 g OM .kg -1 LW 0.75.d -1 . Compared with yearlings, 2-year-old horses had a lower daily foraging time and a higher intake rate (9.9 vs. 7.6 g OM .min -1 ). Grass height had no effect on the food intake of growing horses for grass between 6 and 9 cm high. Compared with cattle and even sheep, horses maintain their lev- els of food intake even at low sward heights. horse / feeding / grass / intake Resume — Alors que le pâturage constitue l'alimentation principale des jeunes chevaux, il n'existe que tres peu de donnees sur les quantites d'herbe ingerees sur les prairies. Dans cette experimenta- tion, trois niveaux de biomasse relativement faibles ont ete proposes aux animaux (respectivement 2,3 ; 2,9 et 3,5 T MS.ha -1 ), ce qui correspond a des hauteurs d'herbe de 6,6 ; 8,1 et 9,4 cm respectivement. Deux categories de poulains de selle (un an et deux ans, respectivement 334 and 478 kg) ont ete integrees a l'etude. L'essai a ete conduit selon un dispositif en carre latin 3 〈 3. Les quantites d'herbe

Two experiments were carried out in Guadeloupe to estimate the organic matter intake (OMI) and digestibility (OMD) of a Dichanthium spp. sward, grazed by tethered Creole heifers [mean live weight (LW) 202 ± 2·0 kg], at three daily herbage allowances. Experiment 1 examined herbage allowances of 16, 25 and 31 kg of dry matter (DM) d–1 on a fertilized sward at 21 days of regrowth whereas, in experiment 2, lower allowances of 11, 15 and 19 kg DM d–1 were examined on the same sward, which was unfertilized and grazed at 14 days of regrowth. In each experiment, the herbage was grazed with three groups of two heifers in a 3 × 3 Latin square design. Sward characteristics were described before grazing. OMI was calculated from total faecal output, and OMD was predicted from the crude protein (CP) content of the faeces. The amount of herbage defoliated by the heifers was also estimated on tillers selected at random. Organic matter intakes were on average 26 g and 19 g OM kg–1 LW, and OMD values were 0·740 and 0·665 for Experiments 1 and 2, respectively, and were not affected by allowance. In Experiment 1, the herbage quality was high [0·50 of leaf and 116 g CP kg–1 organic matter (OM)] for a tropical forage, whereas in Experiment 2, the quality of the herbage (0·27 of leaf and 73 g CP kg–1 OM) was lower. These differences were reflected in differences in intake and digestibility in the two experiments. The experimental tropical Dichanthium spp. swards can have intake characteristics similar to those of a temperate sward.

L'enregistrement automatique de la frequence des bouchees chez les bovins au pâturage est plus difficile a realiser que celui des durees d'ingestion, de rumination, ou meme que celui du nombre de coups de mâchoires par jour. Nous avons teste la faisabilite d'un compteur de bouchees permettant de mesurer automatiquement la frequence des bouchees a partir du bruit d'arrachement de l'herbe, signal vraiment specifique de la bouchee. Cet appareil est base sur l'utilisation de deux capteurs, un microphone etanche place sous la mâchoire inferieure et une bille de mercure placee dans un boitier que l'animal porte autour du cou afin de mesurer l'inclinaison de la tete. Les bouchees sont detectees en temps reel et les donnees stockees en memoire chaque minute, avec un transfert sur ordinateur par voie serie. La validite des donnees enregistrees par l'appareil a ete testee au cours de 11 sequences pour un total de 514 min par comparaison avec un comptage manuel realise au champ. Les tests ont ete realises sur quatre vaches laitieres Holstein en pâturage rationne sur prairies de raygrass anglais (Lolium perenne L.) au stade feuillu. Le biais moyen entre le compteur de bouchees et le comptage manuel a varie selon les sequences de -5,8 a + 3,1 bouchees.min -1 (-12,2 a + 7,5 %), pour une moyenne de -1,6 bouchees.min -1 (-3,3 %). Ce biais semble independant de la hauteur du couvert ou du stade de defoliation de la prairie. La variabilite intra-sequence de ce biais est en moyenne de 3,5 bouchees.min -1 , et n'est pas reliee au nombre de bouchees par minute. Il est donc conclu que l'enregistrement automatique du nombre de bouchees chez les bovins au pâturage a partir du bruit d'arrachement de l'herbe est possible avec un degre de precision satisfaisant. Cependant, une protection supplementaire du microphone et une meilleure standardisation de sa position semblent necessaires avant d'envisager une utilisation en routine de ce compteur de bouchees a des fins experimentales.

This trial aimed at studying the effects and possible interactions between forage particle size and feeding frequency on the site and extent of digestion and ruminal fermentations throughout the day in dairy cows fed mixed diets. Two forage particle sizes (chopped, C, or ground and pelleted, G, dehydrated alfalfa) and two feeding frequencies (two (2) or six (6) times daily) were combined in a 2×2! arrangement. Four mid-lactation cows with cannulae in the rumen and proximal duodenum were used in a 4×4 Latin square design. They were fed at 95% of ad-libitum intake with three hours access to the manger after each meal distribution. On a dry-matter (DM) basis, the four diets consisted of 40% dehydrated whole-crop maize, 4% long perennial ryegrass hay, 25% dehydrated alfalfa and 31% concentrate (69% wheat). Dry-matter intake averaged 22.2 kg day−1. No interaction between forage particle size and feeding frequency was found. Feeding G rather than C diets reduced chewing time (22.4 vs. 26.2 min kg−1 DM), total and ruminal digestibilities of organic matter (OM) and cell-wall constituents (p Increasing feeding frequency did not affect carbohydrate digestion and mean ruminal parameters, although post-feeding variations of pH, osmolality and ammonia concentration were much less pronounced. It is concluded that reduced forage particle size can sharply affect the quantity and the nature of digestive end-products by altering chemical and physical conditions in the rumen. However, the magnitude of this effect is not dependent on the amount of fermentable OM entering the rumen in one meal.

Data from in vivo digestibility trials with four to six horses fed twenty-seven forage-based diets are used to calculate prediction equations for the digestibility of dry and organic matter, based on the crude ash (CA), crude protein (CP) and crude fibre (CF) contents of diets and faeces. The most precise prediction of drymatter digestibility (r.s.d. 5 0·032, R 2 5 0·80) was derived from a multiple regression including faecal (CP, CF) and dietary parameters (CF). Among faecal parameters, CP was the best single predictor of both digestibility (r.s.d. 5 0·040, r 2 5 0·63) and dietary CP content (r.s.d. 5 0·028, r 2 5 0·59). For biological reasons we propose a non-linear model that allows prediction of dry- and organic-matter digestibility from faecal CP content with reasonable precision (r.s.d. 5 0·038, 0·036, r 2 5 0·65, 0·74, respectively). This will be adequate for many studies, especially for free-living animals in rangelands.

Les contrôles physique et métabolique de l’ingestion sont impliqués dans la régulation des quantités ingérées par le ruminant, au pâturage comme à l’auge. Cependant, le pâturage est plus contraignant, car l’animal doit lui-même aller chercher et récolter sa nourriture, ce qui rajoute un contrôle ’comportemental’ de l’ingestion. La quantité d’herbe récoltée dans chaque bouchée peut ainsi varier dans des proportions très importantes, de 10 à 400 mg MO chez les ovins et de 70 à 1610 mg MO chez les bovins (Hodgson 1986). L’étude des processus de préhension de l’herbe pâturée est donc nécessaire pour mieux comprendre et prédire les quantités ingérées par l’animal, déterminant majeur de ses performances. La préhensibilité d’un couvert végétal traduit sa facilité de préhension par l’animal. Elle s’apprécie le plus souvent à travers les caractéristiques de la bouchée de l’animal, qui est l’unité de base de l’ingestion et constitue la composante la plus importante de la vitesse d’ingestion. Elle dépend essentiellement des caractéristiques du couvert végétal (structure spatiale, propriétés mécaniques et teneur en MS), mais dépend également du type d’animal qui le pâture, par son mode de préhension et ses caractéristiques (format, taille et forme de la bouche).

La caractérisation du régime alimentaire des ruminants au pâturage en milieu diversifié (prairies d’association et permanentes) est un verrou méthodologique important dans les études portant sur les relations animal-plantes dans ce type de milieu. Le développement récent de techniques permettant l’identification des végétaux dans des substrats complexes ou dégradés (DNA metabarcoding), basées sur l’analyse de fragments résiduels d’ADN des plantes dans les produits de la digestion, pourrait permettre une innovation méthodologique complémentaire aux méthodes actuelles basées sur les examens micro-histologiques, l’extraction et le dosage des alcanes à longue chaîne contenus dans les cuticules des plantes, ou les méthodes spectrales (spectroscopie en proche Infrarouge), ces méthodes étant fastidieuses, peu précises et mal adaptées aux couverts végétaux complexes. L’objectif de ce travail était de tester l’aspect quantitatif de cette méthodologie, déjà sensible pour apprécier qualitativement la composition d’une ration (Farruggia et al., 2012). Des échantillons de produits de la digestion (contenus ruminaux et fèces) ont été prélevés lors d’expérimentations au cours desquelles des espèces fourragères ont été distribuées à des moutons à l’auge en différentes proportions bien définies (mélanges binaires ray-grass anglais (RGA)-légumineuses à l’INRA de Theix, en 2010 et 2011) ou à des vaches laitières au pâturage dans des proportions mesurées par la méthode des alcanes (mélanges de une à cinq espèces à l’INRA de Rennes en 2012). Ces échantillons ont été analysés par le LECA en utilisant un couple d’amorces universelles ciblant une région variable de l’intron du gène chloroplastique trnL(UAA) des végétaux, un fragment adéquat pour l’identification de l’ADN résiduel dans les produits de la digestion car la région amplifiée est à la fois très courte et très variable selon les espèces. Puis, après séquençage massif de ces fragments, le nombre relatif de séquences obtenues dans le produit PCR pour chaque espèce végétale a été comparé à la proportion relative de ces espèces dans l’alimentation des animaux. Les résultats obtenus à partir des mélanges binaires contrôlés montrent une très bonne quantification des proportions de RGA et de légumineuses ingérées (en %, 0:100, 25:75, 50:50, 75:25 et 100:0) lorsque les analyses de DNA metabarcoding ont été réalisées sur contenus ruminaux, et ceci lors des deux années d’étude (mélanges RGA-luzerne et RGA-trèfle blanc, respectivement) (Fig. 1). Les résultats étaient plus mitigés lorsque les analyses de DNA metabarcoding ont été réalisées sur les fèces, avec une quantification correcte avec le mélange RGA-luzerne, bien que la variabilité soit élevée, mais moins bonne avec le mélange RGA-trèfle blanc pour lequel les proportions de RGA étaient sous-estimées (Fig. 1). Il est encore difficile, à ce stade, de déterminer pourquoi la quantification est de moins bonne qualité avec les fèces qu’avec les contenus ruminaux, mais il semble que l’ADN des fèces soit moins efficacement récupéré. Ceci pourrait s’expliquer par un différentiel dans la digestibilité post-ruminale des espèces ingérées, produisant un biais en raison de la méthode d’extraction de l’ADN utilisée qui tend à favoriser la récupération de l’ADN intracellulaire. Une autre explication pourrait résider dans l'assignation des séquences aux espèces : un certain niveau d'erreur est toléré dans l'assignation pour prendre en compte les erreurs de PCR et séquençage. Les ADN étant plus dégradés dans les fèces, un biais d'assignation pourrait être présent qui n'existe pas avec le contenu ruminal. Les échantillons prélevés en 2012 sur vaches laitières sont en cours d’analyse et complèteront les résultats déjà acquis.

absent

Profitable and Sustainable Grazing Systems- Moving forward with ScienceSession 6: Future Research and Development Priorities for Grassland - Based Livestock Systems – Interactive Discussion Session; absent

absent

absent

Chantier qualité GA; This paper introduces a generic assessment method called pluri-energy analysis. It aims to assess the types of energy used in agricultural systems and their conversion efficiencies. Four types of energy are considered: fossil energy, gross energy contained in the biomass, energy from human and animal labor and solar energy. The method was applied to compare smallholder low-input dairy-production systems, which are common in developing countries, to the high-input systems encountered in OECD countries. The pluri-energy method is useful for analyzing the functioning of agricultural systems by highlighting their modes of energy management. Since most dairy systems in South Mali (SM) are low-input systems, they are primarily based on solar and labor energy types and do not require substantial fossil-energy inputs to produce milk. Farms in Poitou-Charentes (PC) and Bretagne (BR) show intermediate values of fossil-energy use for milk production, similar to that found in the literature for typical European systems. However, fossil-energy use for milk production is higher on PC than BR farms because of a higher proportion of maize silage in the forage area; grazing pastures are more common on BR farms. Farms on Reunion Island (RI) require a relatively large amount of fossil energy to produce milk, mainly because the island context limits the amount of arable land. Consequently, milk production is based on large imports of concentrated feed with a high fossil-energy cost. The method also enables assessment of fossil-energy-use efficiency in order to increase the performance of biological processes in agricultural systems. Comparing the low-input systems represented by SM to the high-input systems represented by RI, PC and BR, an increase in solar-energy conversion, and thus land productivity, was observed due to intensification via increased fossil-energy use. Conversely, though fossil-energy use at the herd level increased milk productivity, its effect on gross-energy conversion by the herd was less evident. Partitioning the total on-farm gross energy produced among animal co-products (milk, meat and manure) highlights the major functions of SM herds, which are managed to produce organic crop fertilizers.

Improving ω3 fatty acid ( FA ) transfer from feed to milk and decreasing milk saturated FA ( SFA ) without increasing trans mono-unsaturated FA are desirable goals. Our objective was to study the effects of supplying two α-linolenic acid ( ALA )-rich feedstuffs in interaction with proportion of concentrate in the diet on milk FA composition. The two ALA sources were extruded linseed ( LIN , 700 g/d) and alfalfa protein concentrate ( APC , 2 kg/d), supplying 115 and 49 g/d ALA, respectively, per cow per day. Two groups of 12 cows paired according to milk yield, milk fat and milk protein contents, lactation rank (primiparous or multiparous), lactation stage, DMI, milk proportions of saturated and polyunsaturated FA were fed a corn silage-based diet with 30% ( C30 ) or 65% ( C65 ) cereal-based concentrate and received the 2 ALA sources in a reversal design during 5-wk periods. The cows averaged 117±14 DIM at the beginning of the experiment. Data were analyzed according to a split-plot design using the Proc mixed procedure. There was no significant interaction between the concentrate level and ALA source for most measured parameters. Treatment C65 decreased milk fat content (−1.15%), milk fat yield (−301 g/d), and proportion of SFA, especially C16:0, C18:0, C4:0, C6:0 and C8:0, and increased trans -C18:1, especially t9, t10 and t12. Treatment C65 significantly increased milk yield (+3.7 kg), milk protein content (+0.16%) and milk protein yield (+141 g/d), decreased casein-to-protein ratio (−2.6 percentage units). Compared to LIN, APC increased milk fat content (0.33%), milk fat yield (76 g/d), proportion of SFA, especially C4 to C12, C14:0 and C16:0, and decreased cis and all trans C18:1 isomers. APC tended to decrease milk yield (0.9 kg/d, P =0.061) although DMI was not affected, and did not affect protein yield. APC increased both total protein and total casein contents without impact on casein-to-protein ratio and milk protein yield. The transfer rate of C18:3 from feed to milk was much higher in APC treatment than in LIN treatment (15.3% vs 4.7%). This trial shows that adding ALA-rich feedstuffs to the diet to enrich milk can have very marked effects on milk FA composition but also on milk protein composition. These effects are stronger with high concentrate diets, resulting in acidogenic risk. The rate of transfer of ALA from feed to milk also varies according to lipid source. Higher transfer rates lead to lower modifications of milk composition.

REDNEX Merged Deliverables

La prairie pâturée, source de nutriments la plus économique pour les vaches laitières, devrait constituer la base de systèmes économes et durables. Dans ces systèmes, la gestion de l’alimentation des troupeaux laitiers au pâturage est un challenge majeur. L’objectif de cet article de synthèse est de présenter et de hiérarchiser les principaux facteurs déterminant des apports énergétiques et azotés des vaches laitières au pâturage en milieu tempéré, afin de mettre en évidence les voies d’actions possibles permettant des performances par vache élevées tout en maximisant l’utilisation et la valorisation de l’herbe par hectare. La gamme de variation possible des besoins alimentaires des vaches et de leur capacité d’ingestion est comparée avec celle de la valeur alimentaire des prairies pâturées et des effets induits par la gestion du pâturage. Ces comparaisons montrent que les vaches fortes productrices ne peuvent pas atteindre leur potentiel de production laitière lorsqu’elles sont nourries à l’herbe seule. Les bilans énergétiques théoriques des vaches peuvent cependant être estimés dans une large gamme de disponibilité et de qualité de prairies. Des modèles prévisionnels permettent aussi de calculer les apports de concentrés nécessaires pour couvrir ces besoins dans une large gamme de pratiques. Les effets de la pression de pâturage, de la complémentation, de l’utilisation des légumineuses ou de la gestion du temps d’accès journalier au pâturage sont notamment présentés et discutés. Il est conclu que les connaissances acquises en termes de régulation de l’ingestion et de la digestion des vaches laitières au pâturage permettent aujourd’hui de définir les voies de maîtrise de l’alimentation du troupeau et des performances des systèmes laitiers bovins herbagers., Grazed pasture is the cheapest source of nutrients for dairy cows and should form the basis of profitable and low input animal production systems. Management of high producing dairy cows at pasture is thus a major challenge in most countries. The objective of the present paper is to review the factors affecting nutrient supply for grazing dairy cows in order to point out areas with scope for improvement on managing variations in nutrient supply to achieve high animal performance while maintaining efficient pasture utilisation per hectare. Reviewing the range in animal nutrient requirements, intake capacity and pasture nutritive values shows that high producing cows cannot satisfy their energy requirements from grazing alone. Favourable to unfavourable situations for grazing dairy cows may be defined according to pasture quality and availability. Predictive models also enable to calculate supplementation level required to meet energy requirements in various situations. Solutions to maintain acceptable level of production per cow and high output per ha are discussed. Strategies of concentrate supplementation and increasing use of legumes in mixed swards are the most promising. It is concluded that there is scope for improving animal performance at grazing given recent developments in our understanding of factors influencing pasture intake and digestion

Five multiparous Holstein cows were used in a study with a 5 x 5 Latin square design to measure the effects of postruminal infusion of Met on lactational performance and plasma metabolites. The treatments were duodenal infusions of 1) 10 g/d of Lys (control), 2) 10 g/d of Lys plus 6 g/d of Met, 3) 10 g/d of Lys pus 12 g/d of Met, 4) 10 g/d of Lys plus 18 g/d of Met, and 5) 10 g/d of Lys plus 24 g/d of Met. The cows were fed a diet of 61% maize silage, 31% concentrate, and 5% dehydrated alfalfa. The DMI were similar among treatments. Milk yield, 4% FCM, and milk fat yield and content were not affected by infusions. In contrast, milk protein yield and content were increased linearly as Met infusion increased, which was true also for plasma Met and Cys concentrations. Using measurements of AA flow to the duodenum and assumed intestinal digestibilities of 0.8 for digesta and 1.0 for infused AA, estimated concentrations of Lys and Met in total AA absorbed in the small intestine were 7.3% for Lys and 1.52, 1.73, 1.94, 2.15, and 2.36% for Met for diets 1 through 5, respectively. The substantial linear increases in milk protein yield and content indicated that postruminal Met supply was not adequate over the entire range of Met infusions. In conclusion, the extent of Met limitation in this study could be defined only as that exceeding 2.4% of total AA absorbed in the small intestine.

L'effet de la quantite d'herbe allouee (DHA = biomasse (HM) x surface offerte journellement (DOA)) et des caracteristiques des animaux sur les quantites de MO d'herbe ingerees au pâturage (HOMI) ont ete analysees au cours de deux essais. Dans l'essai 1, deux niveaux de DHA (Bas et Moyen, 19 et 26 kg MO/vache/jour) ont ete compares dans un schema en continu en utilisant deux groupes de cinq vaches appariees. Dans le second essai, trois niveaux d'herbe allouee (Bas, Moyen et Haut ; 19, 29 et 46 kg/jour) ont ete compares dans un schema en carre latin 3 x 3 en utilisant trois lots de cinq vaches. Tous les animaux etaient en milieu de lactation et six primipares ont ete utilisees par essai. A la mise a l'herbe, la production de lait a 4 % (FCMt) et le poids vif (LW) variaient de 17 a 35 kg/jour et de 510 a 680 kg. Les vaches n'ont pas recu de concentre et ont ete conduites en pâturage rationne sur prairies de ray-grass anglais pendant toute la duree des essais. La biomasse coupee au niveau du sol a varie de 3,5 a 7,1 t MO/ha entre les periodes. Dans l'essai 1, HOMI (13,5 versus 14,9 kg/j) et la production de lait 4 % (20,6 versus 22,0 kg/jour) ont eu tendance a augmenter entre le traitement Bas et Moyen mais les differences n'ont pas ete significatives. Dans l'essai 2, HOMI a augmente de maniere curvilineaire (13,8 ; 16,2 ; 16,7 kg/jour) et la production de lait 4 % a augmente lineairement avec le niveau d'herbe allouee (20,4 ; 21,7 et 23,0 kg/jour). HOMI a toujours ete beaucoup plus faible pour les vaches primipares que les vaches adultes et des differences interindividuelles importantes sont apparues pour un meme rang de lactation. A partir de l'ensemble des donnees individuelles nous avons montre que HOMI peut etre predite a partir de DHA et des caracteristiques des animaux : HOMI = 7,9 - 98 DHA -1 + 0,264 FCMt + 0,0073 LW (n = 95, R 2 = 0,60, etr = 1,77 kg). Cependant, la precision de ce modele est sensiblement amelioree lorsque l'on considere separement les deux composantes de DHA : HOMI = -20,4 - 115 DCA -1 + 9,63 HM - 0,873 HM 2 + 0,266 FCMt + 0,0095 LW (R 2 = 0,70, etr = 1,56 kg). Ces relations montrent que HOMI est affectee par DHA mais aussi que la biomasse et/ou la structure initiale de la prairie affecte egalement les quantites ingerees. De plus les quantites ingerees augmentent avec le potentiel de production des animaux et cet accroissement couvre environ les deux tiers des besoins supplementaires de production pour des pâturages de bonne qualite.

Chantier qualité GA; Emergy accounting (EmA) was applied to a range of dairy systems, from low-input smallholder systems in South Mali (SM), to intermediate-input systems in two regions of France, Poitou-Charentes (PC) and Bretagne (BR), to high-input systems on Reunion Island (RI). These systems were studied at three different levels: whole-farm (dairy system and cropping system), dairy-system (dairy herd and forage land), and herd (animals only). Dairy farms in SM used the lowest total emergy at all levels and was the highest user of renewable resources. Despite the low quality of resources consumed (crop residues and natural pasture), efficiency of their use was similar to that of industrialised inputs by intensive systems in RI, PC and BR. In addition, among the systems studied, SM dairy farms lay closest to environmental sustainability, contradicting the usual image of high environmental impact of cattle production in developing countries. EmA also revealed characteristics of the three intensive systems. Systems from RI and PC had lower resource transformation efficiency and higher environmental impacts than those from BR, due mainly to feeding strategies that differed due to differing socio-climatic constraints. Application of EmA at multiple levels revealed the importance of a multi-level analysis. While the whole-farm level assesses the overall contribution of the system to its environment, the dairy-system level is suitable for comparison of multi-product systems. In contrast, the herd level focuses on herd management and bypasses debates about definition of system boundaries by excluding land management. Combining all levels highlights the contribution of livestock to the global agricultural system and identifies inefficiencies and influences of system components on the environment.

Following recent publication of data on its environmental impact, beef production is being strongly challenged. However, these data concern global ruminant production, which is highly diverse and does not necessarily correspond to the European and French situations. While it is undeniable that ruminant production contributes to global warming, there are several ways of mitigating greenhouse gas emissions, and permanent pastures serve as carbon sinks. Beef production is also a vital economic sector for many regions, where it would not be possible to produce cereals or to develop intensive animal production systems. Beef production also contributes to many collective services, justifying its continued financial support.

Chantier qualité GA; Fossil energy analysis, also called cumulative energy demand, is a current method for environmental assessment of agricultural systems. It consists of assessing fossil energy directly consumed on the farm and indirectly consumed to produce farm inputs. Application of the method is based on the sum of the quantity of each farm input multiplied by its energy coefficient, which represents fossil energy use during the life cycle of the input, including extraction, manufacturing and disposal of the raw and auxiliary materials. The range of values for energy coefficients proposed in the literature and variability in their context of application challenges the confidence in estimates of fossil energy use. To offer an initial representation of this uncertainty and to propose improvements for including uncertainty in energy coefficients, a fossil energy analysis completed by uncertainty and sensitivity analyses was applied to dairy farms from two differing French territories: Poitou-Charentes (PC) and Reunion Island (RI). Monte-Carlo simulation of 30,000 sets of coefficients randomly drawn from the ranges of values found in the literature shows a 95% confidence interval ranging from 3.6 to 5.0 MJ L−1 of raw milk for PC and 5.8-8.2 MJ L−1 of raw milk for RI. This represents a variation around the mean of ±16% for PC and ±17% for RI. This also highlights the need for a standardized and clearly defined method for calculating energy coefficients, especially regionally adapted ones, to accurately estimate fossil energy use of agricultural systems throughout the world. Calculation of a more accurate energy coefficient could be associated with a preliminary sensitivity analysis performed with minimum and maximum values of energy coefficients from the literature to identify the most influential coefficients and adapt them to local conditions. This avoids time-consuming adaptation of all energy coefficients, but requires accurate information about life-cycle inputs. Since energy coefficients are not the only source of uncertainty in fossil energy analysis, however, other guidelines are provided, especially concerning data inputs.

Chantier qualité GA; Environmental impact assessment of agriculture has received increased attention over recent decades, leading to development of numerous methods. Among them, three deal with energy use: Energy Analysis (EA), Ecological Footprint (EF) and Emergy synthesis (Em). Based on a review of 197 references applying them to a variety of agricultural systems, this paper evaluates their ability to assess energy use. While EF assesses energy use as land use via a global accounting approach in which energy is only one component of the assessment, EA and Em are energy-focused and appear more appropriate to highlight ways to increase energy-use efficiency. EA presents a clear methodology via fossil energy use and its associated impacts but does not consider all energy sources. With inclusion of natural and renewable resources, Em focuses on other energy resources, such as solar radiation and energy from labour, but does not present impact indicators nor establish a clear link between activities and their environmental impacts. Improvements of the EA and Em methods could increase their ability to perform realistic and unbiased energy analysis or the diversity of livestock systems encountered in the world. First, to consider all energy sources, as Em does, EA could include solar radiation received by farm surfaces and energy expenditure by humans and animals to accomplish farm operations. Second, boundaries of the studied system in EA and Em must include draft animals, humans and communal grazing lands. Third, special attention should be given to update and locally adapt energy coefficients and transformities.

Les systèmes de production agricole se sont fortement intensifiés, spécialisés et concentrés au sein de territoires qui se sont eux même fortement spécialisés. Cette évolution répondait à une logique économique en période de faible prix de l’énergie et ou les enjeux environnementaux étaient ignorés. Aujourd’hui ces territoires doivent faire face à la dégradation de leurs écosystèmes avec des atteintes à la qualité des eaux, des sols ou l’appauvrissement de la biodiversité. En particulier le découplage de l’animal et des surfaces conduit à des émissions importantes d’azote réactif. Les systèmes de polyculture-élevage offrent des opportunités pour accroître l’efficience d’utilisation de l’azote au sein des agro systèmes en optimisant les interactions écologiques et le recyclage des éléments et en faisant reposer davantage les systèmes de production sur les valorisations de ressources renouvelables. Ce papier étudie les possibilités de développement d’une polyculture-élevage innovante permettant de limiter le recours aux engrais minéraux de synthèse par l’utilisation généralisée de légumineuses et par le recyclage des effluents d’élevage et de préserver l’azote au sein des systèmes par le choix des rotations incluant de la prairie ou autres cultures fourragères. Ces complémentarités entre productions animales et végétales sont à rechercher à différents niveaux d’organisation depuis l’exploitation, au groupe d’exploitations interagissant, à l’échelle territoriale voire nationale., Agricultural systems became more and more intensified, specialised and concentrated within territories which are themselves strongly specialised. This evolution was economically sound in periods of low price for energy whereas the environmental challenges were largely ignored. Today, these territories must tackle the degradation of their ecosystems with a marked degradation of the quality of water, air, soils and the impoverishment of the biodiversity. In particular, the decoupling between animal and farmland leads to important reactive nitrogen emissions. Conservation-oriented mixed farming systems offer opportunities to increase the efficiency of N utilization within the agro systems by optimising ecological interactions and recycling of elements and by improving utilisation of renewable resources. This paper studies the possibilities of developing innovative mixed farming systems which makes it possible to reduce utilisation of mineral fertiliser by the widespread use of legumes and the recycling of animal wastes and to preserve nitrogen within the system by the choice of rotations including pastures or other forage crops. These complementarities between livestock and crop productions must be sought at various levels of organisation from the individual farm to neighbour farms collaborations, larger territories or even at the national scale.

absent

absent

In regions of intensive pig and dairy farming, nutrient losses to the environment at farm level are a source of concern for water and air quality. Dynamic models are useful tools to evaluate the effects of production strategies on nutrient flows and losses to the environment. This paper presents the development of a new whole-farm model upscaling dynamic models developed at the field or animal scale. The model, called MELODIE, is based on an original structure with interacting biotechnical and decisional modules. Indeed, it is supported by an ontology of production systems and the associated programming platform DIESE. The biotechnical module simulates the nutrient flows in the different animal, soil and crops and manure sub-models. The decision module relies on an annual optimization of cropping and spreading allocation plans, and on the flexible execution of activity plans for each simulated year. These plans are examined every day by an operational management sub-model and their application is context dependent. As a result, MELODIE dynamically simulates the flows of carbon, nitrogen, phosphorus, copper, zinc and water within the whole farm over the short and long-term considering both the farming system and its adaptation to climatic conditions. Therefore, it is possible to study both the spatial and temporal heterogeneity of the environmental risks, and to test changes of practices and innovative scenarios. This is illustrated with one example of simulation plan on dairy farms to interpret the Nitrogen farm-gate budget indicator. It shows that this indicator is able to reflect small differences in Nitrogen losses between different systems, but it can only be interpreted using a mobile average, not on a yearly basis. This example illustrates how MELODIE could be used to study the dynamic behaviour of the system and the dynamic of nutrient flows. Finally, MELODIE can also be used for comprehensive multi-criterion assessments, and it also constitutes a generic and evolving framework for virtual experimentation on animal farming systems.

Providing a well-balanced supply of essential AA (EAA) can serve as an opportunity to reduce the protein intake for dairy cows by increasing the efficiency of metabolizable protein (or PDIE, its equivalent in the INRA feeding system) utilization for milk protein yield. Our objectives were to compare the effect of supplying an "ideal" EAA profile (EAA+) with an imbalanced AA profile (control) at 2 levels of PDIE/NE(L) (net energy for lactation) supplies to study the interaction between PDIE and AA profiles, and to compare this ideal profile with a simple mixture of the 4 most deficient EAA (4 EAA) in the diets of dairy cows. Six lactating multiparous Holstein cows received 6 treatments with 2 different levels of PDIE supplied by diets and AA infusions in the duodenum according to a changeover design with 3-wk periods. Within each PDIE supply level, the cows received 3 different AA infusions in the duodenum according to a 3×3 Latin square design with 1-wk subperiods, which corresponded to the following treatment groups: control (Glu), 4EAA (Lys, Met, His, Leu), and EAA+ (4 EAA plus Ile, Val, Phe, Trp, and Tyr). In the low and high PDIE treatments, diets and infusions provided 54.7 and 64.0 g/Mcal of PDIE/NE(L), respectively, which corresponded to crude protein levels of 13.6 and 15.2%, respectively. High-PDIE supplies increased the milk protein yield by 163 g/d, the milk protein content by 1.4 g/kg, the milk yield by 4.1 kg/d, and the lactose yield by 178 g/d and decreased the PDIE efficiency of utilization by 12.4%, whereas the N efficiency of utilization remained unaffected. Supplying the 2 EAA profiles (4EAA and EAA+) increased the milk protein yield by 67 g/d, the milk protein content by 1.3g/kg, and the milk yield by 0.9 kg/d, whereas the milk fat and milk lactose contents were decreased by 2.4 and 1.6g/kg, respectively. The responses regarding milk yield and its composition were similar whether the cows received the 4 EAA or the EAA+ treatment. The responses were similar for the milk yield and composition whether the EAA were supplied by low- or high-PDIE supplies. In conclusion, the efficiency of PDIE utilization was improved by 6.6% and the N efficiency was improved by 7.0% by correcting the EAA profiles, independent of the level of PDIE supplied. In addition, the increased efficiency observed, associated with provision of the 4 EAA, was similar to the provision of all EAA (EAA+) in this experiment.

International audience; Increasing milk omega-3 fatty acids (FA) content is desirable for human health. Our objective was to study the effect of 2 supplements rich in omega-3 in interaction with the proportion of concentrate in the diet on milk FA composition. The 2 sources of omega 3 were extruded flaxseed (FLAX, 1 kg.d−1) and alfalfa protein concentrate (APC, 2 kg.d−1) supplying respectively 115 and 49 g.d−1 omega-3 per cow. The cows were fed a corn silage based diet with 30% (C0) or 65% (C+) cereal based concentrate. The trial was carried out according a nested reversed design using 24 dairy cows averaging 117 ± 14 DIM with 2 periods of 14 d. Data were analyzed according a split plot design using proc mixed procedure. There was no significant interaction between the level of concentrate and the form of omega-3. C+ largely decreased milk fat content (−1.15 %) and yield (−301 g.d−1), the proportion of saturated FA (especially C16:0, C18:0, C4:0, C6:0 and C8:0) and increased trans C18:1, (especially t9, t10 and t12). Compared with FLAX, APC increased milk fat content (0.33 %), saturated FA (especially C4 to C12, C14:0 and C16:0) and decreased cis and all trans C18:1 isomers. Actually, FLAX induced high levels of cis and trans C18:1 isomers, c9t11CLA and C18:2 isomers. Transfer rate of C18:3 from feed to milk was much higher for APC (15.3 vs 4.7%) and increased with C+ when FLAX was fed. Decrease in milk fat content with C+ is classical and is due to the large amount of concentrate that had probably increased rumen propionic acid and t10 FA. It seems that these nutrients could have had a negative additive effect on milk fat content and yield. Especially, t10 FA could have inhibited FA synthesis in mammary gland. Decrease in milk fat content with FLAX is a consequence of heat seed treatment that increases oil release in the rumen, limiting ruminal biohydrogenation and inducing more trans FA. Positive effect of APC on transfer rate could be due to its manufacturing process inducing a lipid-proteic coagulum protecting FA. The effect of nature and protection of lipids on biohydrogenation depends on level of concentrates.

International audience; Decision support tools to help dairy farmers gain confidence in grazing management need to be able to predict performance of grazing animals with easy-to-obtain variables on farm. This paper, the second of a series of three, describes the GrazeIn model predicting herbage intake for grazing dairy cows. The model of voluntary intake described in the first paper is adapted to grazing situations taking account of sward characteristics and grazing management, which can potentially affect intake compared to indoor feeding. Rotational and continuously stocked grazing systems are considered separately. Specific effects of grazing management on intake were quantified from an extensive literature review, including the effect of daily herbage allowance and pre-grazing herbage mass in rotational grazing systems, sward surface height in continuously stocked grazing systems, and daily time at pasture in both grazing systems. The model, based on iterative procedures, estimates many interactions between cows, supplements, sward characteristics and grazing management. The sensitivity of the prediction of herbage intake to sward and management characteristics, as well as the robustness of the simulations and an external validation of the GrazeIn model with an independent data set, is presented in a third paper.

L'évaluation environnementale des systèmes de production est devenu un enjeu important afin de définir les pistes favorisant le développement de systèmes plus efficients et plus respectueux de l'environnement. C'est pour mieux évaluer ces systèmes et les adaptations que l'on peut y apporter que le modèle MELODIE a été développé. En proposant une architecture générique originale faisant interagir un modèle simulant le pilotage et un modèle simulant les processus biotechniques, MELODIE offre la possiblité de décrire le fonctionnement de systèmes d'élevage très différents. Il permet de comparer différents scénarios de conduite des élevages et de les évaluer à même structure d'exploitation et contexte pédo-climatique. Les nombreuses possibilités de sorties du modèle en font un outil particulièrement intéressant pour l'expérimentation virtuelle sur les systèmes d'élevage, complémentaire des approches par expérimentation systèmes ou suivis d'exploitations.

Le contexte environnemental actuel, tant politique (objectifs de réduction des émissions de gaz à effet de serre) que sociétal (information du consommateur), nécessite de préciser les impacts de l'activité d'élevage bovin en matière de changement climatique. L'enjeu est de connaître précisément les niveaux d'émissions de gaz à effet de serre (GES) et de stockage de carbone, des différents modes de production. Pour cela, une évaluation basée sur la méthodologie de l'Analyse du Cycle de Vie (ACV) est mise au point à l'échelle du système d'élevage. Cette approche permet d'avoir une vision globale de l'activité d'élevage intégrant l'ensemble des processus internes et externes au fonctionnement de l'exploitation. Ainsi pour les systèmes laitiers français, l'empreinte carbone brute du lait est en moyenne de 1,26 kg CO2/kg de lait. La prise en compte du stockage de carbone sous les prairies et les haies se traduit par une compensation comprise entre 6 et 43% selon les systèmes, en fonction de la part de prairies. L'empreinte carbone nette du lait français est alors en moyenne de 1,0 kg CO2/kg de lait. Dans les systèmes bovins viande français, l'empreinte carbone brute est comprise entre14,8 et 16,5 kg CO2/kg viande vive en fonction du système de production (naisseur vs naisseur/engraisseur). Après prise en compte du stockage de carbone qui permet une compensation comprise entre 24 et 53%, l'empreinte carbone nette est comprise entre 7,9 et11,3 kg CO2/kg viande vive. De nombreux leviers d'action sont identifiés dans les systèmes d'élevage de ruminants pour réduire l'empreinte carbone des produits au portail de la ferme. Certains concernent une optimisation des systèmes de production (ajustement des apports alimentaires, gestion de la fertilisation…) et se traduisent par des économies en matière d'intrants. D'autres nécessitent la mise en place de nouvelles technologies et se traduiront donc par un investissement ou un coût de fonctionnement supérieur aux schémas actuels de production., In today's environmental context, as much political (the reduction of greenhouse gas emissions) as social (consumer demands for information concerning food products), there is a need to determine the influence of ruminant livestock on climate change. It has become crucial to quantify precisely the levels of greenhouse gas emissions (GHG) and carbon sequestration for different ruminant livestock systems by using Life Cycle Assessment (LCA) to calculate the carbon footprint of dairy and beef farms. This approach allows us to account for GHG in relation with direct and indirect emissions. Thus in the French dairy system, the average gross carbon footprint is 1.26 kg CO2 /kg milk. Carbon sequestration under grassland and hedges compensates for GHG emissions ranging from 6 to 43% according to the system utilized. Consequently the net carbon footprint is 1.0 kg CO2 / kg milk. In the French beef system, the gross carbon footprint for raw materials is comprised between 14.8 and 16.5 kg CO2 / kg of live meat depending on the production system. It must be mentioned that carbon sequestration represents compensation in a range of 24 to 53% and the net carbon footprint is between 7.9 and 11.3 kg CO2 / kg of live meat. These investigations demonstrate that numerous mitigation actions have been identified in the livestock systems to reduce the carbon footprint of milk and meat at the farm gate. Some of them concern management practices (adjustment of dietary intake, fertilization management...) which result in substantial savings in agricultural expenses. Others require the installation of new technologies which would require additional funds to improve the production processes.

International audience; GrazeIn is a model for predicting herbage intake and milk production of grazing dairy cows. The objectives of this paper are to test its robustness according to a planned arrangement of grazing and feeding scenarios using a simulation procedure, and to investigate the precision of the predictions from an external validation procedure with independent data. Simulations show that the predicted effects of herbage allowance, herbage mass, herbage digestibility, concentrate supplementation, forage supplementation and daily time at pasture are consistent with current knowledge. The external validation of GrazeIn is investigated from a large dataset of twenty experiments representing 206 grazing herds, from five research centres within Western Europe. On average, mean actual and predicted values are 14 center dot 4 and 14 center dot 2 kg DM d-1 for herbage intake and 22 center dot 7 and 24 center dot 7 kg d-1 for milk production, respectively. The overall precision of the predictions, estimated by the mean prediction error, are 16% (i.e. 2 center dot 3 kg DM d-1) and 14% (i.e. 3 center dot 1 kg d-1) for herbage intake and milk production, respectively. It is concluded that the GrazeIn model is able to predict variations in herbage intake and milk production of grazing dairy cows in a realistic manner over a wide range of grazing management practices, rendering it suitable as a basis for decision support systems.

International audience; Several reports, directives, regulations and initiatives challenge high-input dairy systems at the environmental level. At the same time the dairy sector has to adapt to a greater volatility of prices and to the projected increase in energy and fertiliser prices. In this new context, it should be considered whether the model of development based on intensification, often in connection with the reduction in the use of grazing, is always well adapted. Dairy systems that maximise grass utilisation appear to be highly competitive and the various roles of grassland in providing regulating and supporting services are now widely recognized. Thus grassland should form the basis of more sustainable dairy systems in the future, provided technical innovations are produced to improve the efficiency of grassland-based dairy systems. Innovations in forage production, innovations in characteristics of the cows and management of lactations, as well as innovations in the management of the system have potential for increasing economic and environmental performances of grassland-based systems. The more systematic use of legume forages in multi-species swards makes it possible to reduce the consumption of mineral N, to reduce the carbon footprint of the dairy system, to regularize the forage production over the year and to increase the nutritional quality of the forages. It clearly appears that intensive selection for milk based on high concentrate diets has generally resulted in genotypes that are not well suited for systems maximising forage utilisation. In these systems there needs to be a special focus to address fertility, survival and other functional traits such as mastitis resistance, although high genetic merit for milk should be maintained to produce efficient responses to concentrate supply. Finally, extending the grazing season with early turnout or late grazing, and tactical use of grazing in association with conserved forages in large herds, offers many opportunities to reduce the requirement of expensive conserved forage and to reduce the utilisation of purchased feeds. All these potential sources of progress are discussed.

International audience

National audience

Rumen acidosis raises specific issues in intensive farming. It is therefore desirable to have indicators allowing the assessment of the risk of acidosis in diet formulation. To establish theses criterion, several data bases gathered on bovines were analyzed with statistical meta-analyses approaches. This process allows determining prediction equations of mean rumen pH value from various types of measurements. Certain criterion, relevant but difficult to measure on farm, mainly concern the units of research. (chewing index, starch digested into the rumen). Other parameters can be determined in commercial farms from the analysis of the distributed rations. This is for instance the case of the proportion of concentrate in the ration, or better, the content of degradable DM of the ration or NDF resulting from long forages within the DM of the ration which are today easily calculable criteria starting from feed tables. The distinction between ruminal and metabolic acidoses was also considered in this work. For each item the pH value of 6.2 was chosen as a threshold under which the risk of acidosis is becoming a concern. From the nine criterion selected, a simple grid of evaluation was built to assess the risk of acidosis by distinguishing in a simple way, for each criterion, the thresholds and the situations at risk. This grid can be easily added to the computation software to allow an objective evaluation of the risk of acidosis based on the values of the criteria.; L’acidose du rumen soulève des problèmes croissants dans les élevages intensifs. Il est donc souhaitable de pouvoir disposer d’indicateurs simple d’emploi et permettant d’évaluer le risque acidogène des rations dès le moment de leur calcul. Pour établir ces critères, différentes bases de données rassemblées sur des bovins ont été interprétées. Ces interprétations statistiques, par méta-analyses, ont permis de dégager des prédictions du pH moyen du rumen à partir de différentes mesures. Certains critères, pertinents mais difficile à mesurer, relèvent plutôt des unités de recherches (indice de mastication, digestion ruminale de l’amidon). D’autres paramètres peuvent être évalués sur le terrain à partir d’une caractérisation de la ration distribuée ; c’est par exemple le cas de la proportion d’aliments concentrés, ou mieux, de la teneur en MS dégradable de la ration ou du NDF issus de fourrages longs au sein de la Matière Sèche (MS) de la ration qui sont aujourd’hui des critères facilement calculables à partir des tables de la valeur des aliments. La distinction entre les acidoses ruminale et métabolique a aussi été considérée dans ce travail. Pour chaque critère la valeur du pH de 6,2 a été prise comme seuil en dessous duquel le risque d’acidose du rumen était à considérer. A partir des 9 critères retenus, une grille d’évaluation a été proposée en distinguant de façon simple, pour chaque critère, les seuils et les situations à risque. Cette grille peut être facilement ajoutée aux logiciels de calcul des régimes de manière à pouvoir évaluer objectivement le risque d’acidose d’une ration, compte tenu des critères connus.